Active matrix display devices, such as organic electroluminescence (EL) display devices or liquid crystal display devices, have a thin-film transistor (TFT) provided to each of pixels arranged in a matrix.
The thin-film transistor includes, above a substrate, a gate electrode, a semiconductor layer (a channel layer) a source electrode, and a drain electrode. The channel layer typically includes a silicon thin film. The silicon thin film is roughly classified into a non-crystalline silicon thin film (an amorphous silicon thin film) and a silicon thin film (a crystalline silicon thin film) processed with a crystallization treatment.
A thin-film transistor including the crystalline silicon thin film as a channel layer presents greater carrier mobility and better on-state current characteristics than a thin-film transistor including the non-crystalline silicon thin film as a channel layer. Thus, the use of the crystalline silicon thin film is beneficial as a channel layer for a driving transistor since excellent on-state current characteristics are required of thin-film transistors (driving transistors) to drive organic EL elements in an organic EL display device.
One of conventional techniques to form such a crystalline silicon thin film involves irradiating, with a laser beam, an amorphous silicon thin film formed above a substrate to crystallize the amorphous silicon thin film (See Patent Literatures 1 and 2).